Technically,
only animals with sweat glands can sweat. Birds lack them, but being warm-blooded,
they still must have some way to cool down when it's sweltering outside
or they risk meltdown. Short of switching on a fan--which, incidentally,
domesticated pigeons can be trained to do--they accomplish this by means
of a number of thermoregulating strategies. Primarily, birds off-load excess
heat either by evaporative cooling directly through the skin or by panting.
The latter method cools the bird's airways and helps lower an elevated
internal temperature. A robin running across a lawn on a sunny afternoon
with its beak agape is doing exactly that. To supplement panting, several
species vibrate the muscles and bones in their throats, a tactic called
gular fluttering.

Bathing also beats the heat, as does ruffling feathers, seeking shade,
and taking a siesta. Cormorants chill by perching with wings outspread.
Other species, like black kites, ascend on thermals to reach higher, colder
altitudes. Laysan albatrosses simply lean back to expose their feet to
the breeze. Perhaps the most unique heat-dissipating antic belongs to some
storks and New World vultures, which deliberately defecate on their legs.
When the wind blows--voila!--natural air-conditioning. It's messy, but,
hey, it does the trick--no sweat.

Why do June bugs fly around at the same time every
evening?

Sandy Briggs, Ontario, New York

For the same reason that teenagers cruise on Saturday nights: romance.
During a few fleeting weeks in June and July, swarms of ardent European
chafers (which are often mistaken for June bugs) participate in an annual
ritual that not only ensures the perpetuation of their species but also
spells the end of their brief adult lives. Every evening, the beetles set
forth at approximately 8:30, when the sun is slipping below the horizon.
"Once the number of lumens reaches a certain level," says Cornell University
entomologist Paul Robbins, "these guys come boiling out of the ground,
looking for a vertical object to congregate on." And conjugate on. For
the next half-hour, the air is abuzz with their beating wings. They convene
en masse (sometimes by the thousands) around the chosen trysting place--usually
a tree or shrub but occasionally a telephone pole or chimney--then find
partners for a dos-si-do that lasts well into the wee hours. Couples start
falling from the trees at about 10, and flights back home continue throughout
the evening, with stragglers returning at dawn. Each insect has about six
days to fulfill its biological imperative, just the amount of time it takes
to use up all the fat gained during a yearlong larval feeding blitz. Then
it dies.

Any question about the origin of the expression "Crazy as a June bug"?

The leader of an owling walk told me that the
night vision of humans and owls is comparable. True?

Bonnie Campbell, Kalamazoo, Michigan

Unless
you can spot a vole more than a football field away, your night vision
is as similar to an owl's as, well, night is to day. Once the sun sets,
it's no contest. In truth, no creature can see in total darkness. But owls
have a keen sense of sight in dim light, which, coupled with an acute sense
of hearing, makes them superb nighttime hunters. The ancient Greeks believed
the birds' extraordinary vision emanated from a magical inner light. Superstitions
notwithstanding, owls are endowed with ophthalmic assets befitting their
lofty position on the food chain. They possess gigantic eyeballs, which
can better absorb low-level ambient light (if our eyes were proportionate,
they would be as big as grapefruits!). Complementing each super-size orb
is a powerful lens, a broad retina, and a pupil capable of dilating to
a great diameter to collect photons under even the duskiest conditions.
Like other vertebrates, owls have two types of sensory cells in their retinas:
light-sensitive rods and color-sensitive cones. Their retinas are densely
packed with rods, at the expense of cones. Thus, they can better distinguish
small moving objects--albeit, probably in monochrome--while flying beneath
the crepuscular canopy of a forest. Some owl species boast nearly a million
rods per square millimeter (people have about 200,000 per square millimeter).
Furthermore, owl eyes contain a tapetum, a mirror-like membrane that amplifies
light and gives rise to eye shine, the phenomenon that causes your car's
headlights to reflect off of animals' eyes after dark. The birds' sharp
audiovisual system works in concert with silent flight and spatial memory
to keep them from being among those creatures that go bump in the night.